feat: add member and guild tombstones

[steipete]

Summary

• add lossless schema-v5 tombstone metadata and explicit delete/restore paths for guilds and members
• keep refreshes and routine share imports merge-only, with chronological revision handling and tombstone-wins ties
• handle Discord guild/member deletion events without treating unavailable or omitted entities as deleted
• document the lifecycle contract and add the 0.11.8 changelog entry

Proof

• GOWORK=off go test -count=1 -race ./...
• GOWORK=off go test -count=1 ./...
• GOWORK=off go vet ./...
• staticcheck ./...
• golangci-lint run
• gosec -exclude=G101,G115,G202,G301,G304 ./...
• govulncheck ./...
• AutoReview: clean after resolving schema-compatibility and RFC3339 offset findings
• real binary: upgraded a v4 scratch database losslessly, exercised equal/newer tombstone and restore merges, omission safety, forced exact restore, and UTC canonicalization of a newer offset revision

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Exclude tombstones from activity report totals

When a member is tombstoned, store status and member queries now exclude it here, but scanTotals still uses select count(*) from members in internal/report/report.go:107. As a result, discrawl report continues counting every deleted member in its displayed archive size, making it inconsistent with the new member lifecycle and the main status count; apply the same deleted_at is null predicate to the report query.

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